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Developments in Optics and Communications Joint Session International Student Conference Developments in Optics and Communications University of Latvia Riga, Latvia 28 –30 April, 2006 Riga has recently become an attractive venue for international events: concerts, the Ice Hockey World Championship, the NATO summit, to name but a few. Science is no exception. This year, student chapters of two world-renowned scientific organizations have joined forces for the international student conference “Developments in Optics and Communications.” DOC-2006 presents a limited number of papers in the field of modern optics applications, which deal with topics as varied as light–matter interactions and visual perception. For some, this conference is a step to their “DOC”- torate. For others, it is a chance to share their broad academic experience. Yet for everybody it is an opportunity to get a new perspective on the research done in optics and communications. Congratulations on joining science! On behalf of the organizers, Aigars Atvars, President of the Student Chapter, The Optical Society of America Latvian Council of Science TOK project LAMOL (MTKD-CT-2004-01-014228) 2 Email to [email protected] www.spie.org www.osa.org Latvian Council of Science: www.lzp.lv The University of Latvia: www.lu.lv 3 SESSION 1 10:00 R.Erts, A.Atvars Opening speech 10:15 Key speaker (lasers) Laser manipulation of molecular levels and its applications A.Ekers 11:00 Coffee break Key speaker (vision) Feedbacks and Selforganization in Visual Perception: 11:20 M. Ozolinsh Optical illusions 11:40 A. Nikitina Optical Illusions and the special effects of the eye K. Bagucka, Efficiency of eye movements at different reading speeds 12:00 R. Paeglis, I. Lacis 12:20 O. Balcers The relationship study of photoluminescence outcome and detergent optical brighteners water concentration within the context of convenient anthropogenic load indication in effluent. POSTER SESSION G.Bakradze, Study of transition metal impurities influence on optical 12:40 and micromechanical properties of MgO V.Skvortsova 3 + 12:43 M. Hobein , A.Gerdes, The a Σ state of NaK: High resolution spectroscopy to E. Tiemann determine the bound part of the potential 12:46 A. Bulanovs PLZT EFISH nonlinear multiphase modulator 12:49 D. Lauva, M.Ozolish Influence of retinal aftereffects and contrast adaptation in perception of Gabor gratings 12:52 S.Makovejs Raman Amplifiers in Fiber Optical Communication Systems 4 SESSION 2 14:00 A. Podniece, Dynamics of eye movements in recognizing images of R.Paeglis, I. Lacis natural objects 14:20 S. Fomins, V.Karitāns, Saliency based visual attention in the visual search task G.Ikaunieks, M.Ozolinsh 14:40 T. Kirova, E.Ekers Lifetime determination of degenerate molecular levels in et. al. cw regime using the Autler-Townes effect 15:00 M. Auzinsh, K. Coherent Excitation and Quadratic Stark Effect in the Blushs, R. Ferber, F. Cesium Hyperfine Manifold: Level Crossing and Gahbauer, A. Jarmola, Alignment to Orientation Conversion and M. Tamanis 15:20 Coffee Break 15:30 Invited speaker Commercialization of Inventions E. Baltinsh 16:00 Conference Closing, Excursions Modifications to the program are possible 5 LASER MANIPULATION OF MOLECULAR LEVELS AND ITS APPLICATIONS A. Ekers1, T. Kirova1, N. N. Bezuglov2, L. P. Yatsenko3, R. Garcia-Fernandez4, K. Bergmann4 1 Institute of Atomic Physics Spectroscopy, University of Latvia, LV-1586 Riga, LATVIA 2 Fock Institute of Physics, St. Petersburg State University, 198904 St. Petersburg, RUSSIA 3 Institute of Physics of the Academy of Sciences, 03650 Kiev, UKRAINE 4 Deptartment of Physics, University of Kaiserslautern, D-67663 Kaiserslautern, GERMANY The Autler-Townes effect was first described some 50 years ago [1], and it was studied extensively later on. It has enabled important applications in atomic physics, like laser cooling [2], transition dipole moment measurement [3], coherent population transfer schemes (STIRAP) [4], etc. However, for molecules only a few high-resolution studies of the Autler-Townes (AT) effect exist [5]. The present contribution presents high resolution studies of the AT effect in molecules, and proposes novel applications of this effect for the determination of lifetimes and branching ratios of highly excited molecular states. A novel technique The experiments were performed in a Na2 supersonic beam using the cascade 1 + 1 + 1 + 1 + level scheme X Σg → A Σu → 5 Σg (or 6 Σg ) (Fig 1), which represents an open 3- level system. A strong dressing laser couples 1 + 61Σ + two of the levels, while a weak probe monitors 5 Σg g 5s + 3s 4p + 3s the modification of these levels by the dressing v=10, J=9 g field. Three configurations can be distinguished: n i s s e r detection (i) a strong dressing field couples the d 1 + 3p + 3s A Σu intermediate and upper states, and a weak probe v’=10, J’=8 scans across the resonance with the populated e b detection lower level; (ii) a dressing field couples the o r p 3s + 3s lower and intermediate levels, and a probe X1Σ + g v”=0, J”=7 drives the second transition; (iii) strong fields 510 R (a.u.) drive both transitions. In case (i) the splitting of Fig. 1. Cascade scheme in Na , case i. 2 the dressed levels into AT doublets is observed in the probe excitation spectrum. In the weak probe limit the AT spectrum can be used for the determination of lifetimes of the excited states [6]. This approach appears easier 6 than the standard techniques employing time resolved spectroscopy. In the strong probe limit the AT spectrum yields information on the branching ratio of the highly excited states. In case (ii) the probe excitation spectrum differs from the doublet structure observed in closed 3-level systems. It changes from a single narrow line at resonance to a broad spectral structure at moderate detuning of the dressing field, and then again to a narrow line at large detuning. This is explained by a dynamic interplay of the AT effect and optical pumping in an open system. Novel application of this effect for laser manipulation of spatial distribution of excited molecules is proposed. Finally, in the case (iii) the use of two strong laser pulses in a counterintuitive sequence (second transition before the first) allows one to coherently drive the population flow from the ground state through short-lived highly excited molecular levels with efficiencies close to 100% [7]. Support by the European Social Fund, NATO Grant EAP.RIG.981378, and EU FP6 TOK project LAMOL is acknowledged. References [1] S.H. Autler and C.H. Townes, Phys. Rev. 100, 703 (1955). [2] A. Aspect et al., Phys. Rev. Lett. 57, 1688 (1986). [3] M. A. Quesada et al., Phys. Rev. A 36, 4107 (1987). [4] K. Bergmann, H. Theuer and B.W. Shore, Rev. Mod. Phys 70, 1003 (1998). [5] J. Qi et al., Phys. Rev. Lett. 83, 288 (1999); ibid 88, 173003 (2002). [6] R. Garcia-Fernandez, A. Ekers, J. Klavins, et al., Phys. Rev. A 71, 023401 (2005). [7] R. Garcia-Fernandez, A. Ekers, L. P. Yatsenko, et al., Phys. Rev. Lett. 95, 043001 (2005). 7 FEEDBACKS AND SELFORGANIZATION IN VISUAL PERCEPTION: OPTICAL ILLUSIONS M. Ozolinsh Dept. of Optometry and Vision Science, University of Latvia, 8 Kengaraga Str., Riga Eemail: [email protected] Perception and processing of visual information is a tremendous task for humans, and contrary to some other beings like dogs, vision is the dominating information input for decision making. From our previous practice we all know the problems of image processing in computers and different kinds of restrictions to organizing the interchange of visual information with sufficient size and quality. During the past decade, achievements in electronic processing speed and memory density have made possible an unbelievable leap in this area. However that has a cost. Unlike in electronics, where the supply of energy is much easier, and installation of more and more powerful processor cooler fans is possible, the human brain cannot be rebuilt and modified in such a simple way. Visual information perception with immediate processing is organized in several steps within the visual pathway in our brains. In the brain, that is not quite correct, however at the same time still 100% correct. The first stage takes place already in our eyes, physically separate from the brain. However, just in our eyes the primary neural information processing takes place. The eyes are connected with the next “elements” of the pathway (optic chiasm, “the commutator,” and the lateral geniculate nucleus LGN, “The reception office” of the visual cortex) with only a connection bundle of 106 neurons– a one million pin parallel port. The ignition of neural pulses is a “very” slow Can you recognize the object? Where is light coming from? 8 process, the maximum rate being around (3-5)x102 per sec. As they travel along this neural bundle, pulses lose their intensity, and they are regenerated. Crossmodulation trends to take place via biochemical metabolism processes in the bundle neighbourhood. These energy losses and a limit on the rate of the stochastic neural pulse firing in the eye photoreceptors forces a preprocessing of the image already in the eye retina, i.e., coding of luminance and colour, “compressing” the image, and separating information to be sent faster for more precise processing in order to obtain a high spatial resolution. This preliminary processing should be an economic one, smart to fit the needs of perception and to fit the mechanisms of the further neural processing in the visual cortex. A similar job is done in our everyday life digital camera use. We obtain lot of bits from our camera 5Megapixel CCD or CMOS sensor with 14-16 bit depth for each of the RGB colours. All that is processed on-line in the camera to obtain a uniform 5MP size image with only 8 bit depth per colour.
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